This invention relates to shield tunnel boring machines for excavating horizontal tunnels in unstable ground.
Generally, a machine of the type referred to is initially disposed within a pit in the earth made at the tunnel starting point and is then driven to excavate the ground in a horizontal direction in which the tunnel is to be bored, while a steel cylindrical shield effectively prevents the tunnel face ground layer from collapsing. For this reason, the machine should find its remarkable utility specifically when employed in boring a tunnel in the unstable ground of water-bushing, water-containing and highly fluidic ground layers.